This paper uses a non-standard value assumption--uncertainty reduction--to explain parenthood. We begin by reviewing the inadequacies of normative and standard rational choice explanations of shifts in fertility behavior. Then we propose a theory of the value of children based on the uncertainty-reduction assumption. Next we generate a range of hypotheses that follow both from this assumption and from a subsidiary assumption of marital solidarity enhancement. Finally, we explore the extent to which implications based on these new ideas are supported by the relevant empirical literature.

Although rational choice theory has made considerable advances in other social sciences, its progress in sociology has been limited. Some sociologists' reservations about rational choice arise from a misunderstanding of the theory. The first part of this essay therefore introduces rational choice as a general theoretical perspective, or family of theories, which explains social outcomes by constructing models of individual action and social context. "Thin" models of individual action are mute about actors' motivations, while "thick" models specify them ex ante. Other sociologists' reservations, however, stem from doubts about the empirical adequacy of rational choice explanations. To this end, the bulk of the essay reviews a sample of recent studies that provide empirical support for particular rational choice explanations in a broad spectrum of substantive areas in sociology. Particular attention is paid to studies on the family, gender, and religion, for these subareas often are considered least amenable to understanding in terms of rational choice logic.

The origin of values and preferences is an unresolved theoretical question in behavioral and social sciences. The Savanna-IQ Interaction Hypothesis, derived from the Savanna Principle and a theory of the evolution of general intelligence, suggests that more intelligent individuals may be more likely to acquire and espouse evolutionarily novel values and preferences (such as liberalism and atheism and, for men, sexual exclusivity) than less intelligent individuals, but that general intelligence may have no effect on the acquisition and espousal of evolutionarily familiar values (for children, marriage, family, and friends). The analyses of the National Longitudinal Study of Adolescent Health (Study 1) and the General Social Surveys (Study 2) show that adolescent and adult intelligence significantly increases adult liberalism, atheism, and men's (but not women's) value on sexual exclusivity.

General intelligence (g) poses a problem for evolutionary psychology's modular view of the human brain. The author advances a new evolutionary psychological theory of the evolution of general intelligence and argues that general intelligence evolved as a domain-specific adaptation for the originally limited sphere of evolutionary novelty in the ancestral environment. It has accidentally become universally important merely because we now live in an evolutionarily novel world. The available data seem to support the author's contention that intelligent people can solve problems better than less intelligent people only if the problems are evolutionarily novel, and they have no advantage in solving evolutionarily familiar problems. This perspective can also solve some empirical anomalies, such as the "central theoretical problem of human sociobiology" (D. R. Vining, 1986, p. 167) and the geographic distribution of general intelligence throughout the world.The g factor is actually a biologically based variable, which, like other biological functions in the human species, is necessarily a product of the evolutionary process. (Jensen, 1998, p. xii) I thank Garth J. O. Fletcher for disagreeing with me, thereby motivating me to write this article, and

Wilkinson contends that economic inequality reduces the health and life expectancy of the whole population but his argument does not make sense within its own evolutionary framework. Recent evolutionary psychological theory suggests that the human brain, adapted to the ancestral environment, has difficulty comprehending and dealing with entities and situations that did not exist in the ancestral environment and that general intelligence evolved as a domain-specific adaptation to solve evolutionarily novel problems. Since most dangers to health in the contemporary society are evolutionarily novel, it follows that more intelligent individuals are better able to recognize and deal with such dangers and live longer. Consistent with the theory, the macro-level analyses show that income inequality and economic development have no effect on life expectancy at birth, infant mortality and age-specific mortality net of average intelligence quotient (IQ) in 126 countries. They also show that an average IQ has a very large and significant effect on population health but not in the evolutionarily familiar sub-Saharan Africa. At the micro level, the General Social Survey data show that, while both income and intelligence have independent positive effects on self-reported health, intelligence has a stronger effect than income. The data collectively suggest that individuals in wealthier and more egalitarian societies live longer and stay healthier, not because they are wealthier or more egalitarian but because they are more intelligent.